SERUM THYROGLOBULIN MEASUREMENT IN CONGENITAL HYPOTHYROIDISM DETECTED BY NEONATAL SCREENING: CONTRIBUTION TO THE ETIOLOGICAL DIAGNOSIS

PAPENDIECK P,; CHIESA A,; BALLERINI G,; ROPELATO MG,; GRUÑEIRO-PAPENDIECK L

Viña del Mar Chile

Congreso; XVIII Reunion Anual de la Sociedad Latinoamericana de Endocrinologia Pediatrica; 2006

SLEP

Thyroglobulin (Tg), the most abundant thyroid specific protein, is a key precursor in the production of thyroid hormone. In the absence of thyroid damage, the major determinants of its serum concentration are thyroid cell mass and TSH stimulation. It has been proposed as a tool for etiological diagnostic approach of congenital hypothyroidism (CH). To assess the usefulness of serum Tg measured by a sensible method in the etiologic evaluation of CH, TSH, T4, T3 by ECLIA, thyroid antibodies and Tg by IFMA ( detection limit 0,9 ng/ml) were determined in 66 newborns detected by screening. They were classified according to their Tc 99 thyroid scan and ultrasound in 1) ectopic (n:28), 2) athyreotic a) with coincident ultrasound (n:12) b) with discordant ultrasound (n:5) and 3) eutopic a) with goiter (n:16) b) without goiter (n:5). For age related reference values Tg was determined in 32 normal infants aged 7 to 50 days. Initial Tg levels (ng/ml) in CH were [(median and (range)]: 1) ectopic 135.5 (17.9 –492), 2) athyreotic a) with coincident ultrasound 0,58 (0,03- 6), b) with discordant ultrasound 65,2 (13,7- 150) and eutopic a) with goiter 1139 (0,9- 2186), b) without goiter 98,6 (40,3- 330). Control group median 41,5, percentile 3 11,5 and percentile 97 99,4. Conclusion: Tg was useful to evaluate CH at the moment of diagnostic confirmation. The finding of normal circulating Tg levels in patients with discordant thyroid scan/ ultrasound suggests a better sensitivity of Tg with respect to the scan in detecting thyroid tissue. Tg appears to be a useful complement in the study of CH at diagnosis allowing a better rational genetic approach to disorders of thyroid formation and differentiation